文留地区石炭-二叠纪煤系生烃史及生烃潜力

Hydrocarbon-generating potential and history of Carboniferous-Permian coal measure strata in Wenliu area

许化政 周新科

Xu Huazheng Zhou Xinke

东濮凹陷文留地区石炭-二叠纪煤系分布稳定、含有机质丰富,是文留气藏可靠的气源岩。煤系在埋藏过程中有两次生烃过程:第一次发生在中、下三叠统沉积后,镜质体反射率()、磷灰石裂变径迹、古流体包裹体分析证实当时煤系的古埋深约为3500m,古地温118℃,古演化程度为=0.80%～0.85%。其后经历了中生代约180Ma以抬升剥蚀为主的历程,煤系生烃中止。早第三纪裂谷发育期间,煤系因埋深加大而进入二次生烃期,并在东营组沉积后达到生烃峰值阶段。主体烃源岩主要分布在文东-前梨园洼陷,埋深5290～6360m。文留地区天然气资源探明程度已达到90%以上,有效供气边界条件清楚。经计算,文留气藏有效供气区石炭-二叠纪煤系生烃量为3253.3×10m,排烃量2657.0×10m,天然气聚集系数为5.92%。

The Carboniferous-Permian coal measure strata in Dongpu sag is a fair source rock unit of Wenliu gas pool due to its stable distribution and high organic content. There are two hydrocarbon-generating periods in the burial history of coal measures. The first one occurs when the T formation is deposited. Vitrinite reflectance, apatite fission track and fluid inclusion analyses indicate that the burial depth of coal measures is about 3500 m, with the palaeotem-perature of 118℃ and of 0.80%-0.85%.Hydrocarbon generation of coal measures was interrupted in the Meso-zoic uplift and erosion period (about 1.8 million years).During the Paleogene rifting period,the coal measures was entered into its secondary hydrocarbon-generating period as the burial depth increases, reaching its hydrocarbon-generating peak after the deposition of Dongying formation. The gas-prone source rock is mainly distributed in the region of Wendong-Qianliyuan, with the buried depth of 5290-6360m. The discovery maturity (percentage of ultimately proven reserve with respect to total resources) of gas resources in Wenliu area is more than 90%. In the effective gas supply area of Wenliu gas pool, the hydrocarbon-generating volume and hydrocarbon-expelling volume of Carboniferous-Permian coal measures are estimated to be 3253.3 million m and 2657.0 million m respectively, with a gas accumulation coefficient of 5.92%.

10.11743/ogg20040407